What is genre? I have asked and asked this question and back in 2018 I found an interesting explanation — but I didn’t note where it came from.
A story is a piece of art that induces different emotions as it is read, or told. Different stories can evoke different patterns, varying types of emotion such as happiness and fear, as well as ramping up the intensity. And then letting it die down again. Those emotional patterns are very different for different genres: horror, romance, mystery, cozy, and so on. Not to mention, ‘literary’ fiction has a completely set of emotions it is trying to induce.
A book that isn’t genre (or literary) is just ‘fiction.’ And it is harder to market because, if it is any good, it will have “types and intensities of emotion” but no-one knows what to expect or whether they will like it. One reason why this is really important is that there are some things people want to know about and avoid. I do not like emotional pornography, or vivid and realistic descriptive porn either. And a problem with some modern fiction is the deliberate effort to raise negative emotions that aren’t part of older patterns, and that don’t get properly worked out. Often these emotions include frustration and disgust, because those are strong emotions, and some people think that’s all that matters. Subverting the reader’s happiness can be a goal. Just… no.
A story I told years ago… I went to see my eighteen-month old grandchild and my son was playing a game with him. I didn’t realize at first that a game was about to start, but baby had a very funny look on his face. Dad was holding the baby close to his chest and suddenly tipped him backwards and let him fall — at least two inches. Baby laughed — and clutched. Rinse and repeat the expectant look and sudden dip. And because I am an obsessive grandmother and watched closely, I saw that baby tried Not to grab instantly. It was very subtle, but definitely part of the game.
When someone creates a new genre what they have managed to do is to create a new but highly satisfying pattern that some subset of readers will enjoy. Mixing an emotional romantic subplot with accurate descriptions of tactical engagement with weapons of terror has a new genre description, tactical romance. Regular romance goes on and on about feelings where tactical romance hasn’t got time. It’s not that the character don’t feel, it’s just that the next thing they feel might be a grenade blast. Changes the way the reader engages.
Genre is like the baby’s game. You know what to expect, and you feel safe but … properly done, the thrill is still there. And daddy can and does invent new ways to play.

PIctures from the National Gallery of Art, Soap Bubbles, Chardin and A Lady Writing, Vermeer, Public domain